One of the greatest threats facing the world today is the increasing proliferation of ballistic missiles and weapons of mass destruction. Despite reductions in the number of weapons deployed by the United States and the former Soviet Union, ballistic missile proliferation continues on a wide scale today and could increase as the technology is transferred. Countries invest in ballistic missiles because they provide the means to project power both in a regional and strategic context and a capability to launch an attack from a distance. A country with no ballistic missiles today can acquire them in a very short period of time, and these missiles could become available to nonstate terrorist groups.
Missile defense technology being developed, tested and deployed by the United States is designed to counter ballistic missiles of all ranges—short, medium, intermediate and long. Since ballistic missiles have different ranges, speeds, size and performance characteristics, the ballistic missile defense system is an integrated, “layered” architecture that provides multiple opportunities to destroy missiles and their warheads before they can reach their targets.
The system's architecture includes: (1) networked sensors (including space-based) and ground and sea based radars for target detection and tracking; (2) ground and sea based interceptor missiles for destroying a ballistic missile using either the force of a direct collision, called “hit-to-kill” technology, or an explosive blast fragmentation warhead; and (3) a command, control, battle management, and communications network providing the operational commanders with the needed links between the sensors and interceptor missiles.
One of the key components of the ballistic missile defense system is the standard missile 3 (SM-3), the latest design of which is the SM-3 Block 1B. It is a ship and/or land based missile used by the U.S. and its allies to intercept short to intermediate range ballistic missiles as part of the Aegis Ballistic Missile Defense System. Radar locates the ballistic missile and the Aegis weapon system calculates a solution on the target. Once a solution is in place, the missile is launched.
A solid fuel rocket booster launches the SM-3 out of a Mark 41 vertical launching system (VLS). After launch, the missile establishes communication with the launching platform (ship or ground installation) and proceeds towards the target. Once the booster or first stage burns out, it detaches, and a second stage solid-fuel dual thrust rocket motor (DTRM) takes over propulsion through the atmosphere. The missile continues to receive mid-course guidance information from the launching platform and is aided by GPS data.
The second stage rocket motor eventually burns out and detaches and a solid-fuel third-stage rocket motor (TSRM) takes over propulsion. The TSRM can propel the missile above the atmosphere if needed. The TSRM is pulse fired and provides propulsion for the SM-3 until approximately 30 seconds to intercept when the TSRM separates from the kinetic warhead (KW).
The KW is maneuvered using a throttleable divert and attitude control system (TDACS). The KW searches for the target using pointing data from the launching platform. The KW's sensors identify the target and attempt to identify the most lethal part of the target. The TDACS maneuvers the KW into the target for the final hit-to-kill impact. The KW provides 130 megajoules (96,000,000 ft·lbf, 31 kg TNT equivalent) of kinetic energy at the point of impact.
The KW often contains radar or optics used to detect and pinpoint the location of the target. The divert and attitude control system (DACS), such as the TDACS used with the SM-3 Block 1B missile, uses the information provided by the radar, optics, and other sensors to actuate thrusters and maneuver the KW into the target.
The DACS can maneuver the KW in various ways such as “diverting” the trajectory of the KW or adjusting the attitude (pitch, roll, and yaw) of the KW. Divert movements are typically performed to move the KW sideways or otherwise adjust its trajectory. Attitude adjustments are performed to control the orientation of the KW with respect to an inertial frame of frame or another entity, which is usually the target. For example, the DACS can adjust the attitude of the KW to position radar, optics, and other sensors towards the target. Divert maneuvers typically require substantially more total impulse than attitude adjustment maneuvers.
Although conventional DACS technologies, such as those used in the SM-3 Block 1B TDACS, have served us well, they also suffer from a number of performance deficiencies in the following areas: (1) operating time, (2) energy management (on/off capability), (3) mass, and (4) divert distance. Accordingly, it would be desirable to provide a DACS system that improves operating time, mass fraction, and performance, cost and mission assurance while maintaining the storability, safety and insensitivity advantages of a solid propulsion system.